US2200915A - Combustion air regulating means for fireboxes - Google Patents

Description

May 14, 1940.

v. CLARK COMBUSTION AIR REGULATING MEANS F OR FIBEBOXES I 2 Sheets-Sheet 1 L lI L llllll |lr H EIIYI llluwlll/ f V Filed March 29, 1938 V. F. CLARK May 14, 1940.

COMBUSTION AIR REGULATING MEANS FOR FIBEBOXES Filed March 29. 1938 2 Sheets-Sheet 2 Patented May 14, 1940 UNITED- STATES COMBUSTION AIR REGULATING lVIEANS FOR FIREBOXES Verdrie F. Clark,

New Albany, 1 nd assignor to Peerless Manufacturing Corporation, Louisville, Ky., a corporation of Kentucky Application March 29, 1938, Serial No. 198,750

2 Claims.

This invention relates to means for regulating the supply of combustion supporting air to stokerfed, solid-fuel-burning furnaces or the like, particularly, but not necessarily of the underfeed type in which feeding of the fuel is automatically controlled by the demand on the furnace or the like, and has for its general object to provide a simple, inexpensive, easily installed, reliable and emcient air supply regulating means which is controlled by the condition of the fuel bed in the furnace or the like to insure the supply of approximately the proper amount of air to said fuel bed to maintain an approximately ideal condition thereof during all periods of operation of the furnace or the like.

Another object of the invention is to provide a means for the purpose stated which is adjustable for proper operation in any given installation and for any given setting of the thermostat, aquastat, pressure responsive device or other device by which feeding of the fuel is automatically controlled.

With the foregoing and other objects in view, which will become more fully apparent as the nature of the invention is better understood, the same consists in the novel features of construction, combination and arrangement of parts as will be hereinafter more fully described, illustrated in the accompanying drawings and defined in the appended claims.

In the accompanying drawings, wherein like characters of reference denote corresponding parts in the different views:

Figure l is a side elevation, partly in section, of an underfeed, stoker-fed stoker equipped with the present combustion-air supply regulating means.

Figure 2. is a top plan view of the assemblage shown in Fig. 1.

Figure 3 is an enlarged side elevation, partly in section, of a portion of the air tunnel and the air flow regulating dampers of the invention; and

Figure 4 is a top plan view of the assemblage shown in Fig. 3.

Referring to the drawings in detail, A designates, generally, a firebox or pot which, within the purview of the invention, may have a variety of specifically different forms, and B designates, generally, a means for feeding fuel to the firebox or pot A from a supply bin or the like C and which, within the purview of the invention, may likewise have a variety of specifically different forms.

As illustrated in box or pot A is of prises an open-top retort In series of tuyeres i I.

Spaced outwardly from and surrounding the tuyeres H, is a wall l2 which may comprise a downward extension of the uppermost tuyere and which defines a closed-top, open bottom air space the present instance, the firethe underfeed type and comsurmounted by a driving the same, and operation l3 around the tuyeres from which air may enter the firebox or pot through openings M in the tuyeres.

The retort H)v is disposed within a plenum chamber or wind-box l5, and the wall I? rests at its bottom on the top wall of said plenum cham'ber or wind-box l5 outwardly of an opening it in said top wall through which the upper portion of the retort ID extends and which is of greater diameter than the said upper portion of said retort. Ac.- cordingly, air supplied to the plenum chamber or wind-box I5 is free to flow therefrom into the air space 13 surrounding the tuyeres H and through the openings 14 in said tuyeres into the firebox.

A fuel supply tube 11 is connected with a bottom portion of the retort Ill and leads to said retort from any suitable source of fuel supply, as, for example, the bin C, and in said tube is a screw it or any other suitable means for conveying coal or other fuel to the retort I0 and delivering it upwardly through the open top thereof into the firebox or pot proper comprised by the tuyres l i. As will be understood, an electric motor (not shown) is suitably geared to the screw it for of said motor is controlled by a thermostat, aquastat, pressure responsive device or the like, depending upon whether the installation is for air or water heating or steam generating purposes, so that fuel is delivered periodically to the firebox or pot A in accordance with the demand for heat, this being in accordance with well known practice and being deemed therefore not to require illustration nor more extended description.

Driven by the same motor which drives the screw [8 or, if preferred, by a separate motor under the same control as the screw driving motor, is a fan or blower l9 which may. have any convenient location and which is connected with the plenum chamber or wind-box I5 by an air duct 26 so as to periodically supply combustion air to the fire in harmony with the periodic supply of fuel thereto.

The general combination so far described in which a fuel supply means and a combustion air supply means operate in harmony with each other to deliver fuel and air to a firebox or the like periodically in accordance with the demand for heat, is well known and operates satisfactorily if the time periods between successive operations are of short duration and the condition of the fuel bed does not appreciably change during such time periods. However, there are frequent time periods of more or less long duration between successive operations of the fuel feeding and air supply means when holes may burn in the fuel bed. Then, when the next operation occurs, the air rushes through the holes in the fuel bed, delivers excess oxygen to the fire at localized pointsywhich results in a dearth of oxygen at other points, and, in general causes an inefficient combustion condition in the firebox.

The means comprising the present invention is specially designed not only to insure againstany prolonged rush of air at high velocity through A holes which may burn in a fuel bed, but to assure at all times the supply of approximately the correct amount of air to the full bed to properly sup-' port'combustion of the fuel under all conditions,

of operation of the furnaceor the like, sothat an 7 approximately ideal condition of thefire is C0 1-v stantly maintained.

shaft 23 which extends transversely of the air duct 20 at or near the top thereof and is journaled in the duct side walls or in suitable bearings carried by said side Walls.

One end of the shaft 23 is provided with an arm 24 which extends at right angles, or at substantially right angles, to said shaft and which may appropriately be provided by a bent end portion of said shaft. This arm is disposed outwardly of the adjacent side wall of the duct 20 and is provided for cooperation with a stop 25 to limit opening movement of the damper 2|. The stop 25 is carried by a segmental plate 26 which is'disposed between the arm 24 and the adjacent side wall of the duct 20 and which is mounted in any suitable manner, as upon the shaft 23 or upon one of its bearings, for rotatable adjustment about the axis of said shaft.

may be varied to predetermine the limit of opening movement of the damper 2|.

Any suitable means may be provided to secure the plate 26 in any desired position of adjust ment. In the present instance said plate is provided with an arcuate slot 2'! through which ex,- tends a stud 28 which is fixed with respect to the air duct 20 and which has threaded thereon, outwardly of said plate 26, a wing nut 29. When the nut is loosened the plate is free to be normally adjusted, and by then tightening the nut the plate is clamped in its adjusted position against the adjacent side of the air duct. 'On the side wall of the air duct are indices 3|] and on the plate 26 is a pointer 3| for cooperation with said indices to afford an indication of the limit of opening movement of the damper 22 for any given adjustment of the plate 26. Obviously, this arrangement may be reversed by providing the indices 30 on the plate 26 and by providing any suitable fixed pointer for cooperation with such indices.

The damper 2| tends constantly, under the in fluence of gravity, to swing to a position closing the air duct 20, and it is swingable by the pressure thereagainst of combustion air supplied through said duct by the fan or blower to an open position.

The damper 22 is mounted at or near its top on a horizontal shaft 32 which extends transversely of the air duct 20 at or near the top thereof and is journaled in the duct side walls or in suitable bearings carried by said side walls.

One end of the shaft 32 is provided with an arm 33 which extends at right angles, or at substantially-rightangles, to said shaftandwhich may segmental plate Essentially, the present air supply regulating' means comprises a pair of freely swingable, cooperating dampers 2| and 22 mounted in the air,

Accordingly, by rotatably adjusting the plate 26 the position of the stop 25 other words, by a proper appropriately be provided by a bent end portion of saidshaft. This arm 33 is disposed at substantially right angles to the damper 22, or in any other suitable relationship thereto, and, is

suitably Weighted, as indicated at 34, so as to tend constantly to swing said damper upwardly and rearwardly with respect to the direction of air flow through the duct '20, to a fully or partly open position vas determined by engagement of the arm 33 with an adjustable stop 35 which, as in the case of the stop 25, may be carried by a 36 rotatable about the axis of the shaft 32 and capable of being clamped indifferent rotatably adjusted positions by a wing nut 37 on a stud 38 extending from the adjacent side wallof the air duct 20 through an arcuate slot 39 in said plate.

A suitable fixed stop, such as a lug 40 on the duct 20 to be engaged by the arm 33, is provided to prevent swinging movement of the damper 22 from a fully or partly open position thereof beyond a position in which it closes, or substantially closes, the air duct 20, and, in order to indicate the limit of opening'movement of said damper, asdetermined by adjustment of the plate 36 and the stop'35 carried thereby, said plate 36 is provided with a pointer 4| for cooperation with a series of indices 42 on .the adjacent sidewall of the duct 20. Moreover, the weight 34 is adjust able along the arm 33" to require the exertion of more or less pressure against the damper 22 to swing same to its closed position. To this end, the weight 34 may comprise, as shown, a pair of cooperating lock nuts threaded on the arm 33, or

simply a body of metal slidable along said arm and capable of being secured in adjusted position by a set screw, in accordance practice.

The free end portion 22 of the damper 22 is inclined downwardly or' forwardly to the general plane of said damper so that when the latter is in a fully or partly open position the said portion 22 is disposed to have air, driven through the duct 26 by the fan or blower I 9, impinge against the rear face thereof. Accordingly, dependent upon the adjustment of the weight 34 and a more or less fully open position of the damper as determined by adjustment of the stop 35, a greater or lesser velocity of air flow through the duct 20 will be required to swing said damper to closed position. l

The air duct 20 may be specially constructed to have the dampers 2| and 22 and their related parts associated therewith, or said dampers and their related parts may be assembled with a suitable casing 43 to be applied to the duct 20 in any suitable manner after cutting an opening'in with well known the duct to admit the dampers thereto. In the latter case, which is a convenient manner of applying the dampers to the air ducts of old installations, the walls of the casing 43 become, to all intents and purposes, parts of the Walls of the duct 20; Accordingly, it will be understood that when reference is made herein to the Walls of the air duct, such walls may be either the walls of the duct itself or the walls of a casing or equivalent element such as the casing 43.

V The ideal condition in' the firebox A is a'state of incandescence at all times when the fuel feeding means and the combustion air supply means are operating, and this condition may substantially'be assured by a proper adjustment of the weight 34 along the arm 33 to obtain a properbalance between the air supply and the fuel supply. In adjustment of the weight locity will result in swinging of the damper 22 toward closed position, reducing the volume of air reaching the fire and consequently retarding combustion and permitting the amount of fuel in the firebox to increase. With increase of fuel in the fire box the flow of air bed is retarded and the resulting back pressure created in the air duct 20 results in a reduction in the velocity of the supplied air. The weight 34 then acts to further open the damper 22 and to restore the balanced condition between the air supply and the fuel supply.

The operations recounted may occur at more or less frequent intervals and to greater or lesser extents whenever the fuel feeding means and the air supply means are in operation, with the result, as is apparent, that although the condition of the fire may fluctuate slightly, it never deviates greatly from an ideal incandescent, or substantially ideal incandescent condition.

As long as air is being supplied through the duct 25 it holds the substantially balanced damper 2i in an open or partly open position, depending upon the velocity of the air, but as soon as operation of the fuel feeding means and the fan or blower 59 ceases, as when the required amount of heat has been developed, the damper 2i gravitates to closed position and the damper 22 is swung by the weight 3 4 to its open position. The fuel bed then begins toassume a banked condition, and ii the period of inoperativeness of the fuel feeding means and the air supply means is of short duration the inherent character of the fuel bed may not changeappreciably. If, then, the "fuel feeding means and the air supply means again begin operating the result is substantially the same as if there had not occurred any interruption in their operation.v If, on the other hand,

the period of idleness of the fuel feeding means and the air supply means is of a duration .such that holes burn in the banked fuel bed, then, when the fuelieeding means and the air supply means again are operated, the of air through the duct 2!! permitted by the holes in the fuel bed, resultsin the damper 22 being swung to a more or less fully closed position, thereby cutting off or reducing the flow of air to the firebox to extent to permit fuel to be fed to the firebox at is consumed until the holes in-the fuel bed are filled. As said holes become filled and retard the air flow, the damper 22 opens until there is restored a balance between the and the air supply, and when this balance is attained the damper 22 operates as first recounted to substantially maintain the fire in a condition of incandes'cence.

The damper 25 serves two purposes. First, it acts as a banking damper to deny or reduce flow of natural draft to the firebox during periods of idleness of the fuel feeding and air supply means. Second, it serves to predetermine the maximum amount of air to be delivered to the firebox. In

other words, by adjustment of the stop 25 to limit maximum effective cross through the fuel 1 through holes in the soon as it begins, little or no ash is carried into high velocity flow a much more rapid rate than it feeding of the fuel wall thereof, the

the opening movement of the damper 2|, the sectional area of the air duct 2t may be varied that, when the fuel supply means is regulated for operation at lesser than capacity, an excess of combusion air will not be delivered to the firebox.

In addition to its advantages respecting the regulation of draft, the means comprisingthe present invention accomplishes the elimination, or substantially the elimination, of the disadvantages respecting so-called fly as Heretofore, when'holes. burned in the fuel-bed and air rushedthrough-such holes, fine particles of ash were carried into the like, with the result of obstructing the same and insulating their surfaces. However, since, according to the present invention, rush of air "rel-bed ceases practically as the boiler passes, radiators or the like.

Without further description it is thought that the features and advantages of the invention will be readily apparent to those skilled in the art, and it willof course be understood that changes in the form, proportion and minor details of construction may be resorted to, without departing from the spirit of the invention and scope of the appended claims.

I claim:

1. Air flow control means comprising a duct having a top opening, a casing elementdstaohably mounted on said duct in closing relationship .to said top opening, said casing element having side, top and end walls, the top wall of said casing element being disposed above the top wall of said duct, a horizontalpivot member extending transversely of said casing element approximateand may be made such the boiler passes, radiators or ly in the plane of the top wall of the duct, said pivot member being journaled in the side walls of said casing element, a damper mounted upon said pivot element and having portions extending in opposite directions therefrom, one portion to close the space closethe space between said pivot member and the top wall of said casing element when the damper is closed, means tending constantly to swing the damper to an open position in which it extends longitudinally of the duct near the. top

wall thereof, and means whereby air flowing adjacent to the top thereof, said damper having between said pivot member and- .the bottom of the duct and the other portion to 55v pivot disposed transversely relative to the duct portions extending to opposite sides of said pivot,

one portion to close the space between said pivot and the bottom of the duct and the other por- 'tion to closethe space between said-pivot and the top of the duct when the damper is closed, means tending constantly toswing said damper to an open position in which it extends substantially to the duct near the top longitudinally relative free end portion of said first mentioned portion of said damper being formed to extend downwardly when the damper is in its open position extending substantially longitu-. dinallyrelative to the duct so as to be acted upon by air flowing through the predetermined velocity to initiate closing move duct in excess of a ment of the damper.

VERDRIE'F. CLARK.

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